Seismic streamers generally comprise hydrophones which are interconnected by power and data cables and which are housed within long flexible tubes.
A seismic streamer may be up to 6 kilometers in length and therefore is conventionally made up of a large number of sealed elongate modules that are interconnected end to end to make up the streamer. The modules will be connected together through connectors which form end fittings in the modules end which physically secure the modules together and also provide for electrical connections between modules so that data and power can pass freely the length of the streamer. The streamer may also include electronic transmitting apparatus housed in canisters which are located between streamer modules at various stages along the streamer for broadcasting data which is received by the survey vessel.
The length of the streamer and the drag acting thereon as it is towed through the water, necessitates the use of wire or rope load bearing members which typically interconnect the end fittings at opposite ends of a streamer module.
In a typical streamer as shown in U.S. Pat. No. 4,638,469, there are three or four equi-angularly spaced ropes or wires running the length of the module. Alternatively, in U.S. Pat. No. 5,251,182 the ropes are incorporated within the wall of the surrounding tube. A rope or wire member is typically attached to the respective end fitting by means of a cone cast onto the end of the rope or wire, e.g. an epoxy resin cone. The failure point of such an attachment means is unpredictable. Another problem with these types of construction is that the loads in wires or ropes are not evenly distributed as between the wires or ropes when the strand is curved around a storage reel.
A typical streamer module also includes a number of spacers which substantially fill a cross sectional area of the tube. The spacers serve to maintain the internal cross-section of the tube and to keep the rope or wire load-bearing members separated from the power and data cables. The module also contains acoustic units having hydrophones and oil filler blocks. Typically, the streamer is given controlled buoyancy, usually neutral buoyancy by filling the voids within the streamer module by a liquid of a particular density. Paraffinic hydrocarbons have been used for this purpose. For example in U.S. Pat. No. 3,518,677 there is described the use of a gelatinized hydrocarbon having a specific gravity of 0.8 or slightly below.
The disclosure herein provides means for adjusting the buoyancy of a streamer, improved load bearing members, and improved end fitting for the streamer modules.